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CAMPBELL

BIOLOGY Reece • Urry • Cain • Wasserman • Minorsky • Jackson

© 2014 Pearson Education, Inc.

TENTH

EDITION

49 Nervous Systems

Lecture Presentation by

Nicole Tunbridge and

Kathleen Fitzpatrick


Command and Control Center

The human brain contains about 100 billion

neurons, organized into circuits more complex

than the most powerful supercomputers

Powerful imaging techniques allow researchers to

monitor multiple areas of the brain while the

subject performs various tasks

A recent advance uses expression of

combinations of colored proteins in brain cells, a

technique called “brainbow”


Figure 49.1


Concept 49.1: Nervous systems consist of circuits of neurons and supporting cells

By the time of the Cambrian explosion more than

500 million years ago, specialized systems of

neurons had appeared that enables animals to

sense their environments and respond rapidly


The simplest animals with nervous systems, the

cnidarians, have neurons arranged in nerve nets

A nerve net is a series of interconnected nerve

cells

More complex animals have nerves, in which the

axons of multiple neurons are bundled together

Nerves channel and organize information flow

through the nervous system


Figure 49.2

Nerve net

Radial

nerve

Nerve

ring

Eyespot

Brain

Nerve

cords

Transverse

nerve

Brain

Ventral

nerve cord

Segmental

ganglia

Brain

Ventral

nerve

cord

Segmental

ganglia

Anterior

nerve ring

Longitudinal

nerve cords

Ganglia

Brain

Ganglia

Brain

Spinal cord (dorsal nerve cord)

Sensory

ganglia

(a) Hydra (cnidarian) (b) Sea star (echinoderm) (c) Planarian (flatworm) (d) Leech (annelid)

(e) Insect (arthropod) (f) Chiton (mollusc) (g) Squid (mollusc) (h) Salamander

(vertebrate)


Figure 49.2a

Nerve net

(a) Hydra (cnidarian)

Radial

nerve

Nerve

ring

Eyespot

Brain

Nerve

cords

Transverse

nerve

Brain

Ventral

nerve cord

Segmental

ganglia

(b) Sea star (echinoderm)

(c) Planarian (flatworm) (d) Leech (annelid)


Figure 49.2a, b

Nerve net

(a) Hydra (cnidarian)

Radial

nerve

Nerve

ring

(b) Sea star (echinoderm)


Bilaterally symmetrical animals exhibit

cephalization, the clustering of sensory organs at

the front end of the body

The simplest cephalized animals, flatworms, have

a central nervous system (CNS)

The CNS consists of a brain and longitudinal

nerve cords

The peripheral nervous system (PNS) consists

of neurons carrying information into and out of the

CNS


Figure 49.2c

Eyespot

Brain

Nerve

cords

Transverse

nerve

(c) Planarian (flatworm)


Annelids and arthropods have segmentally

arranged clusters of neurons called ganglia


Figure 49.2d, e

Brain

Ventral

nerve cord

Segmental

ganglia

(d) Leech (annelid)

Brain

Ventral

nerve

cord

Segmental

ganglia

(e) Insect (arthropod)


Figure 49.2b

Brain

Ventral

nerve

cord

Segmental

ganglia

(e) Insect (arthropod)

Anterior

nerve ring

Longitudinal

nerve cords

Ganglia

(f) Chiton (mollusc)

Brain

Ganglia

Brain

(g) Squid (mollusc)


Sensory

ganglia

(h) Salamander (vertebrate)


Nervous system organization usually correlates

with lifestyle

Sessile molluscs (for example, clams and chitons)

have simple systems, whereas more complex

molluscs (for example, octopuses and squids)

have more sophisticated systems


Figure 49.2f, g

Anterior

nerve ring

Longitudinal

nerve cords

Ganglia

(f) Chiton (mollusc)

Brain

Ganglia

(g) Squid (mollusc)


In vertebrates

The CNS is composed of the brain and spinal cord

The peripheral nervous system (PNS) is composed

of nerves and ganglia

Region specialization is a hallmark of both

systems


Figure 49.2h

Brain


Sensory

ganglia

(h) Salamander (vertebrate)


Glia

Glial cells, or glia have numerous functions to

nourish, support, and regulate neurons

Embryonic radial glia form tracks along which newly

formed neurons migrate

Astrocytes induce cells lining capillaries in the

CNS to form tight junctions, resulting in a blood-

brain barrier and restricting the entry of most

substances into the brain


Figure 49.3

Capillary CNS Neuron PNS

Schwann cells Microglia Oligodendrocytes Astrocytes Ependymal

cells

VENTRICLE

Cilia


Radial glial cells and astrocytes can both act as

stem cells

Researchers are trying to find a way to use neural

stem cells to replace brain tissue that has ceased

to function normally


Figure 49.4


Organization of the Vertebrate Nervous System

The CNS develops from the hollow nerve cord

The cavity of the nerve cord gives rise to the

narrow central canal of the spinal cord and the

ventricles of the brain

The canal and ventricles fill with cerebrospinal

fluid, which supplies the CNS with nutrients and

hormones and carries away wastes


Figure 49.5

Gray matter

White

matter

Ventricles


The brain and spinal cord contain

Gray matter, which consists of neuron cell bodies,

dendrites, and unmyelinated axons

White matter, which consists of bundles of

myelinated axons


Figure 49.6

Central

nervous

system

(CNS)

Brain

Spinal

cord

Cranial nerves

Ganglia

outside CNS

Spinal nerves

Peripheral

nervous

system

(PNS)


The spinal cord conveys information to and from

the brain and generates basic patterns of

locomotion

The spinal cord also produces reflexes

independently of the brain

A reflex is the body’s automatic response to a

stimulus

For example, a doctor uses a mallet to trigger a

knee-jerk reflex


Figure 49.7

Quadriceps

muscle

Hamstring

muscle

Key Sensory neuron

Motor neuron

Interneuron

Cell body of

sensory neuron in

dorsal root ganglion Gray

matter

White

matter

Spinal cord

(cross section)


The Peripheral Nervous System

The PNS transmits information to and from the

CNS and regulates movement and the internal

environment

In the PNS, afferent neurons transmit information

to the CNS and efferent neurons transmit

information away from the CNS


Figure 49.8

Afferent neurons

Sensory

receptors

Efferent neurons

Internal

and external

stimuli

Autonomic

nervous system

Motor

system

Control of

skeletal muscle

Sympathetic

division

Parasympathetic

division Enteric

division

Control of smooth muscles,

cardiac muscles, glands

PERIPHERAL NERVOUS

SYSTEM

CENTRAL NERVOUS

SYSTEM

(information processing)


The PNS has two efferent components: the motor

system and the autonomic nervous system

The motor system carries signals to skeletal

muscles and is voluntary

The autonomic nervous system regulates

smooth and cardiac muscles and is generally

involuntary


The autonomic nervous system has sympathetic

and parasympathetic divisions

The sympathetic division regulates arousal and

energy generation (4 F’s fight, flight, fright”)

The parasympathetic division has antagonistic

effects on target organs and promotes calming

and a return to “rest and digest” functions


Figure 49.9

Parasympathetic division Sympathetic division

Constricts pupil of eye Dilates pupil of eye

Stimulates salivary

gland secretion

Inhibits salivary

gland secretion

Relaxes bronchi in lungs Constricts

bronchi in lungs

Slows heart Accelerates heart

Inhibits activity of

stomach and intestines

Inhibits activity

of pancreas

Stimulates activity of


Stimulates activity

of pancreas

Stimulates gallbladder

Promotes emptying

of bladder

Promotes erection

of genitalia

Stimulates glucose

release from liver;

inhibits gallbladder

Stimulates

adrenal medulla

Inhibits emptying

of bladder

Promotes ejaculation and

vaginal contractions

Sympathetic

ganglia Cervical

Thoracic

Lumbar

Sacral

Synapse


Figure 49.9a

Parasympathetic division

Constricts pupil of eye

Stimulates salivary

gland secretion

Constricts

bronchi in lungs

Slows heart

Stimulates activity of


Stimulates activity

of pancreas

Stimulates gallbladder

Sympathetic division

Dilates pupil

of eye

Inhibits salivary

gland secretion

Sympathetic

ganglia

Cervical


Figure 49.9b

Sympathetic division

Relaxes bronchi in lungs

Accelerates heart

Inhibits activity of


Inhibits activity

of pancreas

Stimulates glucose

release from liver;

inhibits gallbladder

Stimulates

adrenal medulla

Inhibits emptying

of bladder

Promotes ejaculation and

vaginal contractions

Parasympathetic

division

Promotes emptying

of bladder

Promotes erection

of genitalia

Sympathetic

ganglia

Thoracic

Lumbar

Sacral

Synapse


Concept 49.2: The vertebrate brain is regionally specialized

Specific brain structures are particularly

specialized for diverse functions

The vertebrate brain has three major regions: the

forebrain, midbrain, and hindbrain


Figure 49.UN01

Olfactory

bulb Cerebrum

Cerebellum

Forebrain Midbrain Hindbrain


The forebrain has activities including processing

of olfactory input, regulation of sleep, learning, and

any complex processing

The midbrain coordinates routing of sensory input

The hindbrain controls involuntary activities and

coordinates motor activities


Comparison of vertebrates shows that relative

sizes of particular brain regions vary

These size differences reflect the relative

importance of the particular brain function

Evolution has resulted in a close match between

structure and function


Figure 49.10

Lamprey

Shark

Ray-finned

fish

Amphibian

Crocodilian

Bird

Mammal

ANCESTRAL

VERTEBRATE

Key

Forebrain

Midbrain

Hindbrain


During embryonic development the anterior neural

tube gives rise to the forebrain, midbrain, and

hindbrain

The midbrain and part of the hindbrain form the

brainstem, which joins with the spinal cord at the

base of the brain

The rest of the hindbrain gives rise to the cerebellum

The forebrain divides into the diencephelon, which

forms endocrine tissues in the brain, and the

telencephalon, which becomes the cerebrum


Figure 49.11a


Figure 49.11b

Embryonic brain regions Brain structures in child and adult

Telencephalon

Diencephalon

Mesencephalon

Metencephalon

Myelencephalon Medulla oblongata (part of brainstem)

Pons (part of brainstem), cerebellum

Midbrain (part of brainstem)

Diencephalon (thalamus, hypothalamus, epithalamus)

Cerebrum (includes cerebral cortex, basal nuclei)

Cerebrum Diencephalon Mesencephalon

Metencephalon

Myelencephalon Diencephalon

Telencephalon

Spinal

cord

Child Embryo at 5 weeks Embryo at 1 month

Forebrain

Midbrain

Hindbrain

Hindbrain

Midbrain

Pons

Medulla

oblongata

Cerebellum

Spinal cord

Bra

inste

m

Midbrain

Forebrain


Figure 49.11ba

Embryonic brain regions

Telencephalon

Diencephalon

Mesencephalon

Metencephalon

Myelencephalon Hindbrain

Midbrain

Forebrain

Brain structures in child and adult

Medulla oblongata (part of brainstem)

Pons (part of brainstem), cerebellum

Midbrain (part of brainstem)

Diencephalon (thalamus, hypothalamus, epithalamus)

Cerebrum (includes cerebral cortex, basal nuclei)


Figure 49.11bb

Mesencephalon

Metencephalon

Myelencephalon Diencephalon

Telencephalon

Spinal

cord

Embryo at 1 month

Forebrain

Midbrain

Hindbrain

Embryo at 5 weeks


Figure 49.11bc

Cerebrum Diencephalon

Child

Midbrain

Pons

Medulla

oblongata

Cerebellum

Spinal cord

Bra

inste

m


Figure 49.11c

Cerebrum

Cerebellum

Basal nuclei

Corpus callosum

Cerebral cortex

Right cerebral

hemisphere

Left cerebral

hemisphere

Adult brain viewed from the rear


Figure 49.11d

Diencephalon

Thalamus

Pineal gland

Hypothalamus

Pituitary gland

Spinal cord

Medulla

oblongata

Pons

Midbrain


Arousal and Sleep

The brainstem and cerebrum control arousal and

sleep

The core of the brainstem has a diffuse network of

neurons called the reticular formation

These neurons control the timing of sleep periods

characterized by rapid eye movements (REMs)

and by vivid dreams

Sleep is also regulated by the biological clock and

regions of the forebrain that regulate intensity and

duration


Figure 49.12

Eye

Reticular formation

Input from touch,

pain, and temperature

receptors

Input from

nerves of

ears


Sleep is essential and may play a role in the

consolidation of learning and memory

Some animals have evolutionary adaptations

allowing for substantial activity during sleep

Dolphins sleep with one brain hemisphere at a

time and are therefore able to swim while “asleep”


Figure 49.13

Key

Low-frequency waves characteristic of sleep

High-frequency waves characteristic of wakefulness

Location Time: 0 hours Time: 1 hour

Left

hemisphere

Right

hemisphere


Biological Clock Regulation

Cycles of sleep and wakefulness are examples of

circadian rhythms, daily cycles of biological activity

Such rhythms rely on a biological clock, a

molecular mechanism that directs periodic gene

expression and cellular activity

Biological clocks are typically synchronized to light

and dark cycles


In mammals, circadian rhythms are coordinated by

a group of neurons in the hypothalamus called the

suprachiasmatic nucleus (SCN)

The SCN acts as a pacemaker, synchronizing the

biological clock


Emotions

Generation and experience of emotions involve

many brain structures, including the amygdala,

hippocampus, and parts of the thalamus

These structures are grouped as the limbic system


Figure 49.14

Thalamus

Hypothalamus

Olfactory

bulb

Amygdala Hippocampus


Generating and experiencing emotion often

require interactions between different parts of the

brain

The structure most important to the storage of

emotion in the memory is the amygdala, a mass

of nuclei near the base of the cerebrum


Functional Imaging of the Brain

Brain structures are probed and analyzed with

functional imaging methods

Positron-emission tomography (PET) enables a

display of metabolic activity through injection of

radioactive glucose

Today, many studies rely on functional magnetic

resonance imaging (fMRI), in which brain activity

is detected through changes in local oxygen

concentration


Figure 49.15

Nucleus accumbens Amygdala

Sad music Happy music


Figure 49.15a

Nucleus accumbens

Happy music


Figure 49.15b

Amygdala

Sad music


The range of applications for fMRI include

monitoring recovery from stroke, mapping

abnormalities in migraine headaches, and

increasing the effectiveness of brain surgery


Concept 49.3: The cerebral cortex controls voluntary movement and cognitive functions

The cerebrum, the largest structure in the human

brain, is essential for language, cognition,

memory, consciousness, and awareness of our

surroundings

Four regions, or lobes (frontal, temporal, occipital,

and parietal), are landmarks for particular

functions


Figure 49.16

Motor cortex (control of

skeletal muscles) Somatosensory

cortex

(sense of touch)

Sensory association

cortex (integration

of sensory information)

Frontal lobe

Temporal lobe

Parietal lobe

Occipital lobe

Prefrontal cortex

(decision making,

planning)

Broca’s area

(forming speech)

Auditory cortex

(hearing)

Cerebellum

Visual association cortex (combining images and object recognition)

Visual cortex (processing visual stimuli and pattern recognition)

Wernicke’s area (comprehending language)


Information Processing

The cerebral cortex receives input from sensory

organs and somatosensory receptors

Somatosensory receptors provide information

about touch, pain, pressure, temperature, and the

position of muscles and limbs

The thalamus directs different types of input to

distinct locations


Information received at the primary sensory areas

is passed to nearby association areas that process

particular features of the input

Integrated sensory information passes to the

prefrontal cortex, which helps plan actions and

movements

In the somatosensory cortex and motor cortex,

neurons are arranged according to the part of the

body that generates input or receives commands


Figure 49.17

Frontal lobe

Toes

Lips

Jaw

Tongue Primary motor cortex

Parietal lobe

Genitalia

Primary

somatosensory

cortex Abdominal

organs


Language and Speech

Studies of brain activity have mapped areas

responsible for language and speech

Patients with damage in Broca’s area in the frontal

lobe can understand language but cannot speak

(Broca’s aphasia, non-fluent aphasia)

Damage to Wernicke’s area causes patients to be

unable to understand language, though they can

still speak (Wernicke’s aphasia)


Figure 49.18

Hearing

words

Seeing

words

Max

Min

Generating

words

Speaking

words


Lateralization of Cortical Function

The two hemispheres make distinct contributions

to brain function

The left hemisphere is more adept at language,

math, logic, and processing of serial sequences

The right hemisphere is stronger at facial and

pattern recognition, spatial relations, and

nonverbal thinking


The differences in hemisphere function are called

lateralization

The two hemispheres work together by

communicating through the fibers of the corpus

callosum


Frontal Lobe Function

Frontal lobe damage may impair decision making

and emotional responses but leave intellect and

memory intact

The frontal lobes have a substantial effect on

“executive functions”


Figure 49.UN03


Evolution of Cognition in Vertebrates

Previous ideas that a highly convoluted neocortex

is required for advanced cognition may be

incorrect

The anatomical basis for sophisticated information

processing in birds (without a highly convoluted

neocortex) appears to be the clustering of nuclei in

the top or outer portion of the brain (pallium)


Figure 49.19

Thalamus

Cerebrum

(including pallium)

Cerebellum

Midbrain

(a) Songbird brain

Cerebrum (including

cerebral cortex)

(b) Human brain

Thalamus

Midbrain

Cerebellum


Concept 49.4: Changes in synaptic connections underlie memory and learning

Two processes dominate embryonic development

of the nervous system

Neurons compete for growth-supporting factors in

order to survive

Only half the synapses that form during embryo

development survive into adulthood


Neuronal Plasticity

Neuronal plasticity describes the ability of the

nervous system to be modified after birth

Changes can strengthen or weaken signaling at a

synapse

Autism, a developmental disorder, involves a

disruption in activity-dependent remodeling at

synapses

Children affected with autism display impaired

communication and social interaction, as well as

stereotyped, repetitive behaviors


Figure 49.20

(a) Connections between neurons are strengthened or

weakened in response to activity.

(b) If two synapses are often active at the same time,

the strength of the postsynaptic response may

increase at both synapses.

N1 N1

N2 N2


Memory and Learning

The formation of memories is an example of

neuronal plasticity

Short-term memory is accessed via the

hippocampus

The hippocampus also plays a role in forming

long-term memory, which is later stored in the

cerebral cortex

Some consolidation of memory is thought to occur

during sleep


Long-Term Potentiation

In the vertebrate brain, a form of learning called

long-term potentiation (LTP) involves an

increase in the strength of synaptic transmission

LTP involves glutamate receptors

If the presynaptic and postsynaptic neurons are

stimulated at the same time, the set of receptors

present on the postsynaptic membranes changes


Figure 49.21

(a) Synapse prior to long-term potentiation (LTP) (b) Establishing LTP

(c) Synapse exhibiting LTP

Glutamate

PRESYNAPTIC

NEURON

Mg2+

Ca2+

Na+

NMDA receptor

(open) Stored

AMPA

receptor POSTSYNAPTIC

NEURON

NMDA

receptor

(closed)

1

2

3

1

2

4

3

Action

potential

Depolarization


Figure 49.21a

(a) Synapse prior to long-term potentiation (LTP)

Glutamate

PRESYNAPTIC

NEURON

Mg2+

Ca2+

Na+

NMDA receptor

(open) Stored

AMPA

receptor POSTSYNAPTIC

NEURON

NMDA

receptor

(closed)


Figure 49.21b

(b) Establishing LTP

1

2 3


Figure 49.21c

(c) Synapse exhibiting LTP

Action

potential

Depolarization

1 3

2 4


Concept 49.5: Many nervous system disorders can be explained in molecular terms

Disorders of the nervous system include

schizophrenia, depression, drug addiction,

Alzheimer’s disease, and Parkinson’s disease

These are a major public health problem

Genetic and environmental factors contribute to

diseases of the nervous system

To distinguish between genetic and environmental

variables, scientists often carry out family studies


Figure 49.22

Ris

k o

f d

evelo

pin

g s

ch

izo

ph

ren

ia (

%)

Relationship to person with schizophrenia

Genes shared with relatives of

person with schizophrenia

12.5% (3rd-degree relative)

25% (2nd-degree relative)

50% (1st-degree relative)

100%

50

40

30

20

10

0

Fir

st

co

usin

Ind

ivid

ua

l,

gen

era

l

po

pu

lati

on

Nep

hew

/nie

ce

Un

cle

/au

nt

Gra

nd

ch

ild

Half

sib

lin

g

Pare

nt

Fu

ll s

iblin

g

Ch

ild

Fra

tern

al

twin

Iden

tical

twin


Schizophrenia

About 1% of the world’s population suffers from

schizophrenia

Schizophrenia is characterized by hallucinations,

delusions, and other symptoms

Evidence suggests that schizophrenia affects

neuronal pathways that use dopamine as a

neurotransmitter


Depression

Two broad forms of depressive illness are known

In major depressive disorder, patients have a

persistent lack of interest or pleasure in most

activities

Bipolar disorder is characterized by manic (high-

mood) and depressive (low-mood) phases

Treatments for these types of depression include

drugs such as Prozac, which increase the activity

of biogenic amines in the brain

*SSRI’s like Prozac are not suitable for those with bipolar disorder.


The Brain’s Reward System and Drug Addiction

The brain’s reward system rewards motivation with

pleasure

Some drugs are addictive because they increase

activity of the brain’s reward system

These drugs include cocaine, amphetamine,

heroin, alcohol, and tobacco

Drug addiction is characterized by compulsive

consumption and an inability to control intake


Addictive drugs enhance the activity of the

dopamine pathway

Drug addiction leads to long-lasting changes in the

reward circuitry that cause craving for the drug

As researchers expand their understanding of the

brain’s reward system, there is hope that their

insights will lead to better prevention and

treatment of drug addiction


Figure 49.23

Nicotine stimulates dopamine- releasing VTA neuron.

Inhibitory neuron

Dopamine- releasing VTA neuron

Opium and heroin decrease activity of inhibitory neuron.

Cocaine and amphetamines block removal of dopamine from synaptic cleft.

Reward system response

Cerebral neuron of reward pathway


Alzheimer’s Disease

Alzheimer’s disease is a mental deterioration

characterized by confusion and memory loss

Alzheimer’s disease is caused by the formation of

neurofibrillary tangles and amyloid plaques in the

brain

There is no cure for this disease though some

drugs are effective at relieving symptoms


Figure 49.24

Amyloid plaque Neurofibrillary tangle 20 µm


Parkinson’s Disease

Parkinson’s disease is a motor disorder caused

by death of dopamine-secreting neurons in the

midbrain

It is characterized by muscle tremors, flexed

posture, and a shuffling gait

There is no cure, although drugs and various other

approaches are used to manage symptoms


Figure 49.UN04

L-dopa

Dopa

decarboxylase

Dopamine


Figure 49.UN02

Wild-type hamster

Wild-type hamster with

SCN from 𝜏 hamster

𝜏 hamster

𝜏 hamster with SCN

from wild-type hamster

Before

procedures

After surgery

and transplant

Cir

cad

ian

cycle

peri

od

(h

ou

rs) 24

23

22

21

20

19


Figure 49.UN05

Brain

Sensory

ganglia


Hydra (cnidarian)

Nerve net

Salamander (vertebrate)


Figure 49.UN06

CNS PNS

Astrocyte

Oligodendrocyte

Schwann

cells

Microglial cell Neuron Capillary

Cilia

VENTRICLE

Ependy- mal cell


Figure 49.UN07

Forebrain

Cerebrum

Thalamus

Hypothalamus

Pituitary gland

Pons

Medulla oblongata

Cerebellum

Spinal cord

Midbrain

Hindbrain


Figure 49.UN08

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